Zero padding apparatus for encoding variable-length signaling information and zero padding method using same

ABSTRACT

A zero padding apparatus and method for variable length signaling information are disclosed. A zero padding apparatus according to an embodiment of the present invention includes a processor configured to generate a LDPC information bit string by deciding a number of groups whose all bits are to be filled with 0 using a difference between a length of the LDPC information bit string and a length of a BCH-encoded bit string, selecting the groups using a shortening pattern order to fill all the bits of the groups with 0, and filling at least a part of remaining groups, which are not filled with 0, with the BCH-encoded bit string; and memory configured to provide the LDPC information bit string to an LDPC encoder.

This application is a Continuation of U.S. patent application Ser. No.16/360,409, filed on Mar. 21, 2019, which is a Continuation of U.S.patent application Ser. No. 15/553,908, filed on Aug. 25, 2017, which isa U.S. National Phase application of PCT Application No.PCT/KR2016/001758, filed on Feb. 23, 2016, which claims priority under35 U.S. C. § 119(e), 120 and 365(c) to Korean Patent Application No.10-2015-0028063, filed on Feb. 27, 2015, and Korean Patent ApplicationNo. 10-2016-0020867, filed on Feb. 22, 2016 with the Korean IntellectualProperty Office, the entire disclosures of each of which areincorporated herein by reference for all purposes.

TECHNICAL FIELD

The present invention relates to channel encoding and modulationtechniques for the transmission of signaling information, and moreparticularly to encoding and decoding apparatuses for effectivelytransmitting signaling information in a next generation digitalbroadcasting system.

BACKGROUND ART

Bit-Interleaved Coded Modulation (BICM) is bandwidth-efficienttransmission technology, and is implemented in such a manner that anerror-correction coder, a bit- by-bit interleaver and a high-ordermodulator are combined with one another.

BICM can provide excellent performance using a simple structure becauseit uses a low-density parity check (LDPC) coder or a Turbo coder as theerror-correction coder. Furthermore, BICM can provide high-levelflexibility because it can select modulation order and the length andcode rate of an error correction code in various forms. Due to theseadvantages, BICM has been used in broadcasting standards, such as DVB-T2and DVB-NGH, and has a strong possibility of being used in othernext-generation broadcasting systems.

Such BICM may be used not only for the transmission of data but also forthe transmission of signaling information. In particular, channelencoding and modulation techniques for the transmission of signalinginformation need to be more robust than channel encoding and modulationtechniques for the transmission of data.

Therefore, in particular, there is a pressing need for new channelencoding and modulation techniques for the transmission of signalinginformation.

DISCLOSURE Technical Problem

An object of the present invention is to provide channel encoding andmodulation techniques that are appropriate for the transmission ofsignaling information via a broadcast system channel.

Another object of the present invention is to provide a new zero paddingtechnique that is optimized for the transmission of signalinginformation.

Technical Solution

In order to accomplish the above objects, the present invention providesa zero padding apparatus, including: a processor configured to generatea LDPC information bit string by deciding a number of groups whose allbits are to be filled with 0 using a difference between a length of theLDPC information bit string and a length of a BCH-encoded bit string,selecting the groups using a shortening pattern order to fill all thebits of the groups with 0, and filling at least a part of remaininggroups, which are not filled with 0, with the BCH-encoded bit string;and memory configured to provide the LDPC information bit string to anLDPC encoder.

In this case, the BCH-encoded bit string may correspond to variablelength signaling information.

In this case, each of the groups may include 360 bits, the LDPCinformation bit string may include 3240 bits, and the LDPC encoder maycorrespond to an LDPC codeword whose length is 16200 and whose code rateis 3/15.

In this case, the processor may decide a group which is partially to befilled with 0 using the shortening pattern order, and fill a number ofbits corresponding to a number decided by using the difference betweenthe length of the LDPC information bit string and the length of theBCH-encoded bit string with 0 from the start of the group.

In this case, the shortening pattern order may be defined for 9 groups.

In this case, the shortening pattern order may correspond to an order ofan 8th group indexed as 7, a 9th group indexed as 8, a 6th group indexedas 5, a 5th group indexed as 4, a 2nd group indexed as 1, a 3rd groupindexed as 2, a 7th group indexed as 6, a 4th group indexed as 3, and afirst group indexed as 0.

In this case, the LDPC codeword may be used for parity permutation whichis performed by group-wise interleaving corresponding to an order ofgroup-wise interleaving and a part of parity bits of the LDPC codewordis punctured after the parity permutation.

Furthermore, according to an embodiment of the present invention, thereis provided a zero padding method, including: deciding a number ofgroups whose all bits are to be filled with 0 using a difference betweena length of an LDPC information bit string and a length of a BCH-encodedbit string; selecting the groups using a shortening pattern order;filling all the bits of the groups with 0; and generating the LDPCinformation bit string by filling at least a part of remaining groupswhich are not filled with 0, with the BCH-encoded bit string.

In this case, the BCH-encoded bit string may correspond to variablelength signaling information.

In this case, the zero padding method may further comprise providing theLDPC information bit string to an LDPC encoder.

In this case, each of the groups may include 360 bits, the LDPCinformation bit string may include 3240 bits, and the LDPC encoder maycorrespond to an LDPC codeword whose length is 16200 and whose code rateis 3/15.

In this case, the zero padding method may further comprise deciding agroup which is partially to be filled with 0 using the shorteningpattern order; and filling a number of bits corresponding to a numberdecided by using the difference between the length of the LDPCinformation bit string and the length of the BCH-encoded bit string with0 from the start of the group.

In this case, the shortening pattern order may be defined for 9 groups.

In this case, the shortening pattern order may correspond to an order ofan 8th group indexed as 7, a 9th group indexed as 8, a 6th group indexedas 5, a 5th group indexed as 4, a 2nd group indexed as 1, a 3rd groupindexed as 2, a 7th group indexed as 6, a 4th group indexed as 3, and afirst group indexed as 0.

In this case, the LDPC codeword may be used for parity permutation whichis performed by group-wise interleaving corresponding to an order ofgroup-wise interleaving and a part of parity bits of the LDPC codewordis punctured after the parity permutation.

Furthermore, according to an embodiment of the present invention, thereis provided an inverse zero padding apparatus, including: memoryconfigured to receive an LDPC information bit string from an LDPCdecoder; and a processor configured to select groups whose all bits arefilled with 0 using a shortening pattern order and generate aBCH-encoded bit string from the LDPC information bit string usingremaining groups exclusive of the groups.

In this case, the BCH-encoded bit string may correspond to variablelength signaling information.

In this case, each of the groups may include 360 bits, the LDPCinformation bit string may include 3240 bits, and the LDPC encoder maycorrespond to an LDPC codeword whose length is 16200 and whose code rateis 3/15.

In this case, the shortening pattern order may be defined for 9 groups.

In this case, the shortening pattern order may correspond to an order ofan 8th group indexed as 7, a 9th group indexed as 8, a 6th group indexedas 5, a 5th group indexed as 4, a 2nd group indexed as 1, a 3rd groupindexed as 2, a 7th group indexed as 6, a 4th group indexed as 3, and afirst group indexed as 0.

Advantageous Effects

According to the present invention, the channel encoding and modulationtechniques that are appropriate for the transmission of signalinginformation via a broadcast system channel are provided.

Furthermore, in the present invention, shortening and puncturing areoptimized according to the amount of signaling information in theconstruction of BICM for the transmission of signaling information,thereby being able to efficiently transmit/receive the signalinginformation.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a signaling informationencoding/decoding system according to an embodiment of the presentinvention;

FIG. 2 is an operation flowchart showing a signaling informationencoding method according to an embodiment of the present invention;

FIG. 3 is an operation flowchart showing a signaling informationdecoding method according to an embodiment of the present invention;

FIG. 4 is a diagram showing a broadcast signal frame according to anembodiment of the present invention;

FIG. 5 is a diagram showing the structure of a parity check matrix (PCM)corresponding to an LDPC code according to an embodiment of the presentinvention;

FIG. 6 is a diagram showing an example of the operation of the zeropadding unit shown in FIG. 1;

FIG. 7 is a diagram showing an example of the operation of the paritypermutation unit shown in FIG. 1;

FIG. 8 is a diagram showing an example of the operation of the zeroremoving unit shown in FIG. 1;

FIG. 9 is a block diagram showing a zero padding apparatus according toan embodiment of the present invention; and

FIG. 10 is an operation flowchart showing a zero padding methodaccording to an embodiment of the present invention.

MODE FOR INVENTION

The present invention will be described in detail below with referenceto the accompanying drawings. Repeated descriptions and descriptions ofwell-known functions and configurations that have been deemed to makethe gist of the present invention unnecessarily obscure will be omittedbelow. The embodiments of the present invention are intended to fullydescribe the present invention to persons having ordinary knowledge inthe art to which the present invention pertains. Accordingly, theshapes, sizes, etc. of components in the drawings may be exaggerated tomake the description obvious.

Preferred embodiments of the present invention will be described indetail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a signaling informationencoding/decoding system according to an embodiment of the presentinvention.

Referring to FIG. 1, the signaling information encoding/decoding systemincludes a signaling information encoding apparatus 100, and a signalinginformation decoding apparatus 300.

The signaling information encoding apparatus 100 and the signalinginformation decoding apparatus 300 perform communication through themedium of a wireless channel 200.

The signaling information encoding apparatus 100 channel-encodes andmodulates signaling information, such as L1-Basic, L1-Detail or thelike.

The signaling information encoding apparatus 100 includes a segmentationunit 110, a scrambling unit 120, a BCH encoder 130, a zero padding unit140, an LDPC encoder 150, a parity permutation unit 160, a paritypuncturing unit 170, a zero removing unit 180, a bit interleaving unit190, and a constellation mapping unit 195.

The signaling information encoding apparatus 100 shown in FIG. 1 may beviewed as corresponding to a Bit-Interleaved Coded Modulation (BICM)apparatus. In this case, the error correction encoder of the BICMapparatus may be viewed as corresponding to the segmentation unit 110,the scrambling unit 120, the BCH encoder 130, the zero padding unit 140,the LDPC encoder 150, the parity permutation unit 160, the paritypuncturing unit 170, and the zero removing unit 180 that are shown inFIG. 1.

When the length of the signaling information is longer than a presetlength, the segmentation unit 110 segments the signaling informationinto a plurality of groups in order to segment the signaling informationinto a plurality of LDPC codewords and then transmit the LDPC codewords.That is, when the signaling information cannot be contained in a singleLDPC codeword, the segmentation unit may determine the number ofcodewords in which the signaling information is to be contained, andthen may segment the signaling information according to the determinednumber of codewords.

For example, when the length of the signaling information is fixed likeL1-Basic, the signaling information encoding apparatus 100 may notinclude the segmentation unit 110.

For example, when the length of the signaling information is variablelike L1-Detail, the signaling information encoding apparatus 100 mayinclude the segmentation unit 110.

The scrambling unit 120 performs scrambling in order to protect thesignaling information. In this case, the scrambling may be performedusing various methods that are known in the present technical field.

The BCH encoder 130 performs BCH encoding using a BCH parity whoseparity length N_(bch_Parity) is 168 bits.

In this case, the BCH encoding may be the same as BCH encoding for LDPCcode in which the length of data BICM is 16200.

In this case, a BCH polynomial used for the BCH encoding may beexpressed in Table 1 below, and the BCH encoding expressed in Table 1may have 12-bit error correction capability:

TABLE 1 Code Length N_(ldpc) = 16200 g₁(x) 1 + x + x³ + x⁵ + x¹⁴ g₂(x)1 + x⁶ + x⁸ + x¹¹ + x¹⁴ g₃(x) 1 + x + x² + x⁶ + x⁹ + x¹⁰ + x¹⁴ g₄(x) 1 +x⁴ + x⁷ + x⁸ + x¹⁰ + x¹² + x¹⁴ g₅(x) 1 + x² + x⁴ + x⁶ + x⁸ + x⁹ + x¹¹ +x¹³ + x¹⁴ g₆(x) 1 + x³ + x⁷ + x⁸ + x⁹ + x¹³ + x¹⁴ g₇(x) 1 + x² + x⁵ +x⁶ + x⁷ + x¹⁰ + x¹¹ + x¹³ + x¹⁴ g₈(x) 1 + x⁵ + x⁸ + x⁹ + x¹⁰ + x¹¹ + x¹⁴g₉(x) 1 + x + x² + x³ + x⁹ + x¹⁰ + x¹⁴ g₁₀(x) 1 + x³ + x⁶ + x⁹ + x¹¹ +x¹² + x¹⁴ g₁₁(x) 1 + x⁴ + x¹¹ + x¹² + x¹⁴ g₁₂(x) 1 + x + x² + x³ + x⁵ +x⁶ + x⁷ + x⁸ + x¹⁰ + x¹³ + x¹⁴

After the BCH encoding has been performed, the zero padding unit 140performs zero padding or shortening.

In this case, the zero padding means that part of a bit string is filledwith bit “0.”

As a result of the BCH encoding, the length of the bit string may beexpressed by N_(bch)=K_(sig)+N_(bch_Parity). In this case, K_(sig) maybe the number of information bits of the BCH encoding. For example, whenK_(sig) is fixed to 200 bits, N_(bch) may be 368 bits.

When the LDPC encoder 150 uses an LDPC code whose code rate is 3/15 andwhose length is 16200, the information length K_(ldpc) of the LDPC codeis 3240 bits. In this case, since information that is to be actuallytransmitted is N_(bch) bits and the length of the information part ofthe LDPC code is K_(ldpc) bits, zero padding, i.e., the process offilling bits corresponding to K_(ldpc)−N_(bch) with bit “0,” isperformed.

In this case, the order of the zero padding plays an important role indetermining the performance of the encoder, and the order of the zeropadding may be expressed as shortening pattern order.

In this case, the bits padded with zeros are used only for LDPCencoding, and are not actually transmitted.

The LDPC information bits composed of K_(ldpc) bits is segmented intoN_(info_group) groups, as shown in Equation 1 below. For example, whenK_(ldpc) is 3240, N_(info_group) is 9, and thus the LDPC informationbits may be grouped into 9 groups.

Z _(j) ={i _(k)|360×j≤k≤360×(j+1)} for 0≤j<N _(info_group)  (1)

where Z is a group composed of 360 bits.

The part of K_(ldpc) bits that is zero-padded is determined according tothe following procedure.

(Step 1) First, the number of groups in which all the bits thereof willbe padded with “0” is calculated using Equation 2 below:

$\begin{matrix}{N_{pad} = \lfloor \frac{K_{ldpc} - N_{bch}}{360} \rfloor} & (2)\end{matrix}$

For example, when K_(ldpc) is 3240 and N_(bch) is 368, N_(pad) may be 7.The fact that N_(pad) is 7 indicates that the number of groups in whichall the bits thereof will be padded with “0” is 7.

(Step 2) When N_(pad) is not 0, zero padding is performed on N_(pad)groups in the order of Z_(π) _(s) ₍₀₎,Z_(π) _(s) ₍₁₎, . . . ,Z_(π) _(s)_((N) _(pad) ⁻¹⁾ according to the shortening pattern order π_((s))(j) ofTable 2 below. In this case, π_(s)(j) may refer to the shorteningpattern order of a j-th bit group.

When N_(pad) is 0, the above procedure is omitted.

TABLE 2 π_(s) (j) (0 ≤ j < N_(group)) π_(s) π_(s) π_(s) π_(s) π_(s)π_(s) π_(s) π_(s) π_(s) MODE N_(group) (0) (1) (2) (3) (4) (5) (6) (7)(8) L1- 9 7 8 5 4 1 2 6 3 0 Detail

The shortening pattern order of Table 2 above indicates that zeropadding targets are selected in the order of an 8th group indexed as 7,a 9th group indexed as 8, a 6th group indexed as 5, a 5th group indexedas 4, a 2nd group indexed as 1, a 3rd group indexed as 2, a 7th groupindexed as 6, a 4th group indexed as 3, and a first group indexed as 0.That is, when only 7 groups are selected as zero padding targets in theexample of Table 2 above, a total of 7 groups, i.e., the 8th groupindexed as 7, the 9th group indexed as 8, the 6th group indexed as 5,the 5th group indexed as 4, the 2nd group indexed as 1, the 3rd groupindexed as 2, and the 7th group indexed as 6, are selected as the zeropadding targets.

In particular, the shortening pattern order of Table 2 above may beoptimized for variable length signaling information.

When the number of groups in which all the bits thereof will be paddedwith “0” and the corresponding groups are determined, all the bits ofthe determined groups are filled with “0.”

(Step 3) Additionally, for a group corresponding to Z_(π) _(s)(N_(pad)), bits corresponding to (K_(ldpc)−N_(bch)−360×N_(pad)) from thestart of the group are additionally zero-padded. In this case, the factthat zero padding is performed from the start of the corresponding groupmay indicate that zero padding is performed from a bit corresponding toa smaller index.

(Step 4) After the zero padding has been all completed, an LDPCinformation bit string is generated by sequentially mapping BCH-encodedN_(bch) bits to a remaining part that has not been zero-padded.

The LDPC encoder 150 performs LDPC encoding using K_(ldpc) and which hasbeen zero-padded and to which signaling information has been mapped.

In this case, the LDPC encoder 150 may correspond to an LDPC codewordwhose code rate is 3/15 and whose length is 16200. The LDPC codeword isa systematic code, and the LDPC encoder 150 generates an output vector,such as that of Equation 3 below:

Λ=(c₀,c₁, . . . ,c_(N) _(ldpc) ⁻¹)=(i₀,i₁, . . . ,u_(K) _(ldpc)⁻¹,P₀,P₁, . . . ,P_(16200−K) _(ldpc) ⁻¹)   (3)

For example, when K_(ldpc) is 3240, parity bits may be 12960 bits.

The parity permutation unit 160 performs group-wise parity interleavingon a parity part, not an information part, as a preliminary task forparity puncturing.

In this case, the parity permutation unit 160 may perform parityinterleaving using Equation 4 below:

Y _(j) =X _(j), 0≤j<K _(ldpc)/360

Y _(j) =X _(π(j)) , K _(ldpc)/360≤j<45  (4)

where Y_(j) is a j-th group-wise interleaved bit group, and π(j) is theorder of group-wise interleaving, which may be defined in Table 3 below:

TABLE 3 Order of Group-wise interleaving π(j)(9 ≤ j < 45) 9 10 11 12 1314 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Mode N_(group)33 34 35 36 37 38 39 40 41 42 43 44 L1- 45 16 22 27 30 37 44 20 23 25 3238 41 Detail  9 10 17 18 21 33 35 14 28 12 15 19 11 24 29 34 36 13 40 4331 26 39 42

That is, the parity permutation unit 160 outputs 3240 bits (9 bitgroups) corresponding to information bits among the 16200 bits (45 bitgroups) of the LDPC codeword without change, groups 12960 parity bitsinto 36 bit groups each including 360 bits, and interleave the 36 bitgroups in the order of group-wise interleaving corresponding to Table 3above.

The order of group-wise interleaving of Table 3 indicates that a 17thgroup indexed as 16 is located at a 10th group location indexed as 9, a23rd group indexed as 22 is located at a 11st group location indexed as10, a 28th group indexed as 27 is located at a 12nd group locationindexed as 11, . . . , and a 43rd bit group indexed as 42 is located ata 45th group location indexed as 44.

In this case, the bit group (the bit group indexed as 16) at a frontlocation may correspond to most important parity bits, and the bit group(the bit group indexed as 42) at a rear location may correspond to leastimportant parity bits.

In particular, the order of group-wise interleaving of Table 3 may beoptimized for variable length signaling information.

After the parity interleaving (parity permutation) has been completed,the parity puncturing unit 170 may puncture the partial parities of theLDPC codeword. The punctured bits are not transmitted. In this case,after the parity interleaving has been completed, parity repetition inwhich part of the parity-interleaved LDPC parity bits is repeated may beperformed before parity puncturing is performed.

The parity puncturing unit 170 calculates a final puncturing size, andpunctures bits corresponding to the calculated final puncturing size.The final puncturing size corresponding to the number of bits to bepunctured may be calculated according to the length N_(bch) of theBCH-encoded bit string as follows:

(Step 1) A temporary puncturing size N_(punc_temp) is calculated usingEquation 5 below:

$\begin{matrix}{N_{{punc}\; \_ \; {temp}} = {\lfloor {\frac{A}{2^{n}} \times ( {K_{ldpc} - N_{bch}} )} \rfloor + B}} & (5)\end{matrix}$

where K_(ldpc) is the length of the LDPC information bit string, N_(bch)is the length of the BCH-encoded bit string, A is a first integer, and Bis a second integer.

In this case, the difference K_(ldpc)−N_(bch) between the length of theLDPC information bit string and the length of the BCH-encoded bit stringmay correspond to a zero padding length or a shortening length.

The parameters for puncturing required for the calculation of Equation 5may be defined as in Table 4 below:

TABLE 4 N_(bch) K_(ldpc) A B n N_(ldpc)_parity η_(MOD) L1- 368- 3240 7 01 12960 2 Detail 2520where N_(ldpc_parity) is the number of parity bits of the LDPC codeword,and η_(MOD) is a modulation order. In this case, the modulation ordermay be 2, which is indicative of QPSK.

In particular, the parameters for puncturing of Table 4 may be optimizedfor variable length signaling information.

(Step 2) The temporary number of transmission bits N_(FFC_temp) iscalculated using the calculated temporary puncturing size N_(punc_temp)and N_(ldpc_parity) of Table 4, as shown in Equation 6 below:

N _(FFC_temp) =N _(bch) +N _(ldpc_parity) −N _(punc_temp)  (6)

(Step 3) The number of transmission bits N_(FFC) is calculated using thetemporary number of transmission bits N_(FFC_temp), as shown in Equation7 below:

$\begin{matrix}{N_{FFC} = {\lceil \frac{N_{{FFC}\; \_ \; {temp}}}{\eta_{MOD}} \rceil \times \eta_{MOD}}} & (7)\end{matrix}$

The number of transmission bits N_(FFC) is the sum of the length of theinformation part and the length of the parity part after the completionof the puncturing.

(Step 4) A final puncturing size N_(punc) is calculated using thecalculated number of transmission bits N_(FFC) as shown in Equation 8below:

N _(punc) =N _(punc_temp)−(N _(FEC) −N _(FEC_temp))  (8)

where the final puncturing size N_(punc) is the size of parities thatneed to be punctured.

That is, the parity puncturing unit 170 may puncture the last N_(punc)bits of the whole LDPC codeword on which the parity permutation and therepetition have been performed.

The zero removing unit 180 removes zero-padded bits from the informationpart of the LDPC codeword.

The bit interleaving unit 190 performs bit interleaving on thezero-removed LDPC codeword. In this case, the bit interleaving may beperformed using a method in which the direction in which the LDPCcodeword is recorded in memory of a preset size and the direction inwhich the LDPC codeword is read therefrom are made different.

The constellation mapping unit 195 performs symbol mapping. For example,the constellation mapping unit 195 may be implemented using a QPSKmethod.

The signaling information decoding apparatus 300 demodulates andchannel-decodes signaling information, such as L1-Basic, L1-Detail, orthe like.

The signaling information decoding apparatus 300 includes aconstellation de-mapping unit 395, a bit de-interleaving unit 390, aninverse zero removing unit 380, an inverse parity puncturing unit 370,an inverse parity permutation unit 360, an LDPC decoder 360, an inversezero padding unit 340, a BCH decoder 330, an inverse scrambling unit320, and an inverse segmentation unit 310.

The signaling information decoding apparatus 300 shown in FIG. 1 may beviewed as corresponding to a Bit-Interleaved Coded Modulation (BICM)decoding apparatus. In this case, the error correction decoder of theBICM decoding apparatus may be viewed as corresponding to the inversezero removing unit 380, the inverse parity puncturing unit 370, theinverse parity permutation unit 360, the LDPC decoder 360, the inversezero padding unit 340, the BCH decoder 330, the inverse scrambling unit320 and the inverse segmentation unit 310 that are shown in FIG. 1.

The inverse segmentation unit 310 performs the inverse operation of thesegmentation unit 110.

The inverse scrambling unit 320 performs the inverse operation of thescrambling unit 120.

The BCH decoder 330 performs the inverse operation of the BCH encoder130.

The inverse zero padding unit 340 performs the inverse operation of thezero padding unit 140.

In particular, the inverse zero padding unit 340 may receive an LDPCinformation bit string from the LDPC decoder 350, may select groupswhose all bits are filled with 0 using shortening pattern order, and maygenerate a BCH-encoded bit string from the LDPC information bit stringusing groups exclusive of the former groups.

The LDPC decoder 350 performs the inverse operation of the LDPC encoder150.

The inverse parity permutation unit 360 performs the inverse operationof the parity permutation unit 160.

In particular, the inverse parity permutation unit 360 may segment theparity bits of the LDPC codeword into a plurality of groups, and maygroup-wise de-interleave the groups using the order of group-wiseinterleaving, thereby generating an LDPC codeword that is to beLDPC-decoded.

The inverse parity puncturing unit 370 performs the inverse operation ofthe parity puncturing unit 170.

In this case, the inverse parity puncturing unit 370 may calculate atemporary puncturing size using a first integer, multiplied by thedifference between the length of the LDPC information bit string and thelength of the BCH-encoded bit string, and a second integer differentfrom the first integer, may calculate the temporary number oftransmission bits using the difference between the sum of the length ofthe BCH-encoded bit string and 12960 and the temporary puncturing size,may calculate the number of transmission bits using the temporary numberof transmission bits and modulation order, may calculate a finalpuncturing size using the temporary number of transmission bits, thenumber of transmission bits and the temporary number of transmissionbits, and may generate an LDPC codeword to be provided to the inverseparity permutation unit 360 by taking into account the final puncturingsize.

The inverse zero removing unit 380 performs the inverse operation of thezero removing unit 180.

The bit de-interleaving unit 390 performs the inverse operation of thebit interleaving unit 190.

The constellation de-mapping unit 395 performs the inverse operation ofthe constellation mapping unit 195.

FIG. 2 is an operation flowchart showing a signaling informationencoding method according to an embodiment of the present invention.

Referring to FIG. 2, the signaling information encoding method accordingto the embodiment of the present invention includes segmenting signalinginformation into a plurality of groups first at step S210.

At step S210, when the length of the signaling information is longerthan a preset length, the signaling information is segmented into aplurality of groups in order to segment the signaling information into aplurality of LDPC codewords and then transmit the LDPC codewords. Thatis, when the signaling information cannot be contained in a single LDPCcodeword, the number of codewords in which the signaling information isto be contained may be determined and then the signaling information maybe segmented according to the determined number of codewords at stepS210.

For example, when the length of the signaling information is variablelike L1-Detail, the signaling information encoding method may includestep S210.

For example, when the length of the signaling information is fixed likeL1-Basic, the signaling information encoding method may not include stepS210.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes performing scrambling inorder to protect the signaling information at step S220.

In this case, the scrambling may be performed using various methods thatare known in the present technical field.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes performing BCH encodingusing a BCH parity whose parity length N_(bch_Parity) is 168 bits atstep S230.

Step S230 may be performed by the BCH encoder 130 shown in FIG. 1.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes performing zero padding orshortening after the BCH encoding has been performed at step S240.

In this case, the zero padding may be performed by the zero padding unit140 shown in FIG. 1.

Since information that is to be actually transmitted is N_(bch) bits andthe length of the information part of the LDPC code is K_(ldpc) bits,zero padding, i.e., the process of filling bits corresponding toK_(ldpc)−N_(bch) with bit “0,” is performed at step S240.

The zero padding of step S240 may be performed according to theshortening pattern order of Table 2.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes performing LDPC encodingusing K_(ldpc) and which has been zero-padded and to which signalinginformation has been mapped at step S250.

In this case, step S250 may be performed by an LDPC encodercorresponding to an LDPC codeword whose code rate is 3/15 and whoselength is 16200.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes performing group-wiseparity interleaving on a parity part, not an information part, as apreliminary task for parity puncturing at step S260.

In this case, at step S260, the group-wise parity interleaving may beperformed according to the order of group-wise interleaving of Equation4 and Table 3.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes puncturing the partialparities of the LDPC codeword after the parity interleaving (paritypermutation) has been completed at step S270.

At step S270, the punctured bits are not transmitted.

In this case, after the parity interleaving has been completed, parityrepetition in which part of the parity-interleaved LDPC parity bits isrepeated may be performed before parity puncturing is performed.

The parity puncturing of step S270 may be performed by the paritypuncturing unit 170 shown in FIG. 1.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes performing zero removing,i.e., the process of removing the zero-padded bits from the informationpart of the LDPC codeword, at step S280.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes performing bit interleavingon the zero-removed LDPC codeword at step S290. In this case, step S290may be performed using a method in which the direction in which the LDPCcodeword is recorded in memory of a preset size and the direction inwhich the LDPC codeword is read therefrom are made different.

Furthermore, the signaling information encoding method according to theembodiment of the present invention includes performing symbol mappingat step S295.

FIG. 3 is an operation flowchart showing a signaling informationdecoding method according to an embodiment of the present invention.

Referring to FIG. 3, the signaling information decoding method accordingto the embodiment of the present invention includes performingconstellation de-mapping on a signal received via an antenna at stepS310.

In this case, step S310 may correspond to the inverse operation of stepS295 shown in FIG. 2, and may be performed by the constellationde-mapping unit 395 shown in FIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing bitde-interleaving at step S320.

In this case, step S320 may correspond to the inverse operation of stepS290 shown in FIG. 2, and may be performed by the bit de-interleavingunit 390 shown in FIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing inverse zeroremoving at step S330.

In this case, step S330 may correspond to the inverse operation of stepS280 shown in FIG. 2, and may be performed by the inverse zero removingunit 380 shown in FIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing inverse paritypuncturing at step S340.

In this case, step S340 may correspond to the inverse operation of stepS270 shown in FIG. 2, and may be performed by the inverse paritypuncturing unit 370 shown in FIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing inverse paritypermutation at step S350.

In this case, step S350 may correspond to the inverse operation of stepS260 shown in FIG. 2, and may be performed by the inverse paritypermutation unit 360 shown in FIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing LDPC decoding atstep S360.

In this case, step S360 may correspond to the inverse operation of stepS250 shown in FIG. 2, and may be performed by the LDPC decoder 350 shownin FIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing inverse zeropadding at step S370.

In this case, step S370 may correspond to the inverse operation of stepS240 shown in FIG. 2, and may be performed by the inverse zero paddingunit 340 shown in FIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing BCH decoding atstep S380.

In this case, step S380 may correspond to the inverse operation of stepS230 shown in FIG. 2, and may be performed by the BCH decoder 330 shownFIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing inversescrambling at step S390.

In this case, step S390 may correspond to the inverse operation of stepS220 shown in FIG. 2, and may be performed by the inverse scramblingunit 320 shown in FIG. 1.

Furthermore, the signaling information decoding method according to theembodiment of the present invention includes performing inversesegmentation at step S395.

In this case, step S395 may correspond to the inverse operation of stepS210 shown in FIG. 2, and may be performed by the inverse segmentationunit 310 shown in FIG. 1.

FIG. 4 is a diagram showing a broadcast signal frame according to anembodiment of the present invention.

Referring to FIG. 4, the broadcast signal frame according to theembodiment of the present invention may include a bootstrap 421, apreamble 423, and data symbols 425.

The preamble 423 includes signaling information.

In an example shown in FIG. 4, the preamble 423 may include L1-Basicinformation 431 and L1-Detail information 433.

In this case, the L1-Basic information 431 may be fixed-length signalinginformation.

For example, the L1-Basic information 431 may correspond to 200 bits.

In this case, the L1-Detail information 433 may be variable lengthsignaling information.

For example, the L1-Detail information 433 may correspond to 200 to 2352bits.

An LDPC (low-density parity check) code is known as a code very close tothe Shannon limit for an additive white Gaussian noise (AWGN) channel,and has the advantages of asymptotically excellent performance andparallelizable decoding compared to a turbo code.

Generally, an LDPC code is defined by a low-density parity check matrix(PCM) that is randomly generated. However, a randomly generated LDPCcode requires a large amount of memory to store a PCM, and requires alot of time to access memory. In order to overcome these problems, aquasi-cyclic LDPC (QC-LDPC) code has been proposed. A QC-LDPC code thatis composed of a zero matrix or a circulant permutation matrix (CPM) isdefined by a PCM that is expressed by the following Equation 9:

$\begin{matrix}{{H = \begin{bmatrix}J^{a_{11}} & J^{a_{12}} & \text{⋯} & J^{a_{1n}} \\J^{a_{21}} & J^{a_{22}} & \cdots & J^{a_{2n}} \\\vdots & \vdots & \ddots & \vdots \\J^{a_{m\; 1}} & J^{a_{m2}} & \cdots & J^{a_{mn}}\end{bmatrix}},{{{for}\mspace{14mu} a_{ij}} \in \{ {0,1,\ldots \mspace{14mu},{L - 1},\infty} \}}} & (9)\end{matrix}$

In this equation, J is a CPM having a size of L×L, and is given asEquation 10 below. In the following description, L may be 360.

$\begin{matrix}{J_{L \times L} = \begin{bmatrix}0 & 1 & 0 & \text{⋯} & 0 \\0 & 0 & 1 & \text{⋯} & 0 \\\vdots & \vdots & \vdots & \ddots & \vdots \\0 & 0 & 0 & \cdots & 1 \\1 & 0 & 0 & \cdots & 0\end{bmatrix}} & (10)\end{matrix}$

Furthermore, J^(i) is obtained by shifting an L×L identity matrix I (J⁰)to the right i (0≤i<L) times, and J^(∞) is an L×L zero matrix.Accordingly, in the case of a QC-LDPC code, it is sufficient if onlyindex exponent i is stored in order to store J^(i), and thus the amountof memory required to store a PCM is considerably reduced.

FIG. 5 is a diagram showing the structure of a PCM corresponding to anLDPC code according to an embodiment of the present invention.

Referring to FIG. 5, the sizes of matrices A and C are g×K and(N−K−g)×(K+g), respectively, and are composed of an L×L zero matrix anda CPM, respectively. Furthermore, matrix Z is a zero matrix having asize of g×(N−K−g), matrix D is an identity matrix having a size of(N−K−g)×(N−K−g), and matrix B is a dual diagonal matrix having a size ofg×g. In this case, the matrix B may be a matrix in which all elementsexcept elements along a diagonal line and neighboring elements below thediagonal line are 0, and may be defined as Equation 11 below:

$\begin{matrix}{B_{g \times g} = \begin{bmatrix}I_{L \times L} & 0 & 0 & \cdots & 0 & 0 & 0 \\I_{L \times L} & I_{L \times L} & 0 & \cdots & 0 & 0 & 0 \\0 & I_{L \times L} & I_{L \times L} & \vdots & 0 & 0 & 0 \\\vdots & \vdots & \vdots & \ddots & \vdots & \vdots & \vdots \\0 & 0 & 0 & \cdots & I_{L \times L} & I_{L \times L} & 0 \\0 & 0 & 0 & \cdots & 0 & I_{L \times L} & I_{L \times L}\end{bmatrix}} & (11)\end{matrix}$

where I_(L×L) is an identity matrix having a size of L×L.

That is, the matrix B may be a bit-wise dual diagonal matrix, or may bea block-wise dual diagonal matrix having identity matrices as itsblocks, as indicated by Equation 11 above. The bit-wise dual diagonalmatrix is disclosed in detail in Korean Patent Application PublicationNo. 2007-0058438, etc.

In particular, it will be apparent to those skilled in the art that whenthe matrix B is a bit-wise dual diagonal matrix, it is possible toperform conversion into a Quasi-cyclic form by applying row or columnpermutation to a PCM including the matrix B and having a structure shownin FIG. 5.

In this case, N is the length of a codeword, and K is the length ofinformation.

The present invention proposes a newly designed QC-LDPC code whose coderate is 3/15 and whose codeword length is 16200, as shown in Table 5below. That is, the present invention proposes an LDPC code that isdesigned to receive information having a length of 3240 and generate anLDPC codeword having a length of 16200.

Table 5 shows the sizes of the matrices A, B, C, D and Z of the QC-LDPCcode according to the present invention:

TABLE 5 Code Sizes rate Length A B C D Z 3/15 16200 1080 × 1080 × 11880× 11880 × 1080 × 3240 1080 4320 11880 11880

The newly designed LDPC code may be represented in the form of asequence, an equivalent relationship is established between the sequenceand the matrix (parity bit check matrix), and the sequence may berepresented as shown the following table:

TABLE 1st row: 8 372 841 4522 5253 7430 8542 9822 10550 11896 11988 2ndrow: 80 255 667 1511 3549 5239 5422 5497 7157 7854 11267 3rd row: 257406 792 2916 3072 3214 3638 4090 8175 8892 9003 4th row: 80 150 346 18836838 7818 9482 10366 10514 11468 12341 5th row: 32 100 978 3493 67517787 8496 10170 10318 10451 12561 6th row: 504 803 856 2048 6775 76318110 8221 8371 9443 10990 7th row: 152 283 696 1164 4514 4649 7260 737011925 11986 12092 8th row: 127 1034 1044 1842 3184 3397 5931 7577 1189812339 12689 9th row: 107 513 979 3934 4374 4658 7286 7809 8830 1080410893 10th row: 2045 2499 7197 8887 9420 9922 10132 10540 10816 1187611st row: 2932 6241 7136 7835 8541 9403 9817 11679 12377 12810 12nd row:2211 2288 3937 4310 5952 6597 9692 10445 11064 11272

An LDPC code that is represented in the form of a sequence is beingwidely used in the DVB standard.

According to an embodiment of the present invention, an LDPC codepresented in the form of a sequence is encoded, as follows. It isassumed that there is an information block S=(s₀, s₁, . . . , s_(K−1))having an information size K. The LDPC encoder generates a codewordκ=(λ₀, λ₁, λ₂, . . . , λ_(N−1)) having a size of N=K+M₁+M₂ using theinformation block S having a size K. In this case, M₁=g, and M₂=N−K−g.Furthermore, M₁ is the size of a parity corresponding to the dualdiagonal matrix B, and M₂ is the size of a parity corresponding to theidentity matrix D. The encoding process is performed as follows:

Initialization:

λ_(i) s _(i) for i=0,1, . . . ,K−1

p _(j)=0 for j=0,1, . . . ,M ₁ +M ₂−1  (12)

First information bit λ₀ is accumulated at parity bit addressesspecified in the 1st row of the sequence of the above table. Forexample, in an LDPC code whose length is 16200 and whose code rate is3/15, an accumulation process is as follows:

p₈ = p₈ ⊕ λ₀ p₃₇₂ = p₃₇₂ ⊕ λ₀ p₈₄₁ = p₈₄₁ ⊕ λ₀ p₄₅₂₂ = p₄₅₂₂ ⊕ λ₀p₅₂₅₃ = p₅₂₅₃ ⊕ λ₀ p₇₄₃₀ = p₇₄₃₀ ⊕ λ₀ p₈₅₄₂ = p₈₅₄₂ ⊕ λ₀p₉₈₂₂ = p₉₈₂₂ ⊕ λ₀ p₁₀₅₅₀ = p₁₀₅₅₀ ⊕ λ₀ p₁₁₈₉₆ = p₁₁₈₉₆ ⊕ λ₀p₁₁₉₈₈ = p₁₁₉₈₈ ⊕ λ₀

where the addition ⊕ occurs in GF(2).

The subsequent L−1 information bits, i.e., λ_(m), m=1,2, . . . ,L−1, areaccumulated at parity bit addresses that are calculated by the followingEquation 13:

(x+m×Q₁)mod M₁ if x<M₁

M₁+{(x−M₁+m×Q₂)mod M₂} if x≥M₁  (13)

where x denotes the addresses of parity bits corresponding to the firstinformation bit λ₀, i.e., the addresses of the parity bits specified inthe first row of the sequence of Table, Q₁=M₁/L, Q₂=M₂/L, and L=360.Furthermore, Q₁ and Q₂ are defined in the following Table 2. Forexample, for an LDPC code whose length is 16200 and whose code rate is3/15, M₁=1080, Q₁=3, M₂=11880, Q₂=33 and L=360, and the followingoperations are performed on the second bit λ₁ using Equation 13 above:

p₁₁ = p₁₁ ⊕ λ₁ p₃₇₅ = p₃₇₅ ⊕ λ₁ p₈₄₄ = p₈₄₄ ⊕ λ₁ p₄₅₅₅ = p₄₅₅₅ ⊕ λ₁p₅₂₈₆ = p₅₂₈₆ ⊕ λ₁ p₇₄₆₃ = p₇₄₆₃ ⊕ λ₁ p₈₅₇₅ = p₈₅₇₅ ⊕ λ₁p₉₈₅₅ = p₉₈₅₅ ⊕ λ₁ p₁₀₅₈₃ = p₁₀₅₈₃ ⊕ λ₁ p₁₁₉₂₉ = p₁₁₉₂₉ ⊕ λ₁p₁₂₀₂₁ = p₁₂₀₂₁ ⊕ λ₁

Table 6 shows the sizes of M₁, Q₁, M₂ and Q₂ of the designed QC-LDPCcode:

TABLE 6 Code Sizes rate Length M₁ M₂ Q₁ Q₂ 3/15 16200 1080 11880 3 33

The addresses of parity bit accumulators for new 360 information bitsranging from λ_(L) to λ_(2L−1) are calculated and accumulated fromEquation 13 using the second row of the sequence.

In a similar manner, for all groups composed of new L information bits,the addresses of parity bit accumulators are calculated and accumulatedfrom Equation 13 using new rows of the sequence.

After all the information bits ranging from λ₀ to λ_(K−1) have beenexhausted, the operations of Equation 14 below are sequentiallyperformed from i=1:

p _(i)=p_(i) ⊕p _(i−1) for i=0,1, . . . M ₁−1  (14)

Thereafter, when a parity interleaving operation, such as that ofEquation 15 below, is performed, parity bits corresponding to the dualdiagonal matrix B are generated:

λ_(K+L·t+s)=p_(Q) ₁ _(·s+t) for 0≤s<L, 0≤t<Q₁  (15)

When the parity bits corresponding to the dual diagonal matrix B havebeen generated using K information bits λ₀, λ₁, . . . , λ_(K−1), paritybits corresponding to the identity matrix D are generated using the M₁generated parity bits λ_(K), λ_(K+1), . . . , λ_(K+M) ₁ ⁻¹.

For all groups composed of L information bits ranging from λ_(K) toλ_(K+M) ₁ ⁻¹, the addresses of parity bit accumulators are calculatedusing the new rows (starting with a row immediately subsequent to thelast row used when the parity bits corresponding to the dual diagonalmatrix B have been generated) of the sequence and Equation 13, andrelated operations are performed.

When a parity interleaving operation, such as that of Equation 16 below,is performed after all the bits ranging from λ_(K) to λ_(K+M) ₁ ⁻¹ havebeen exhausted, a parity corresponding to the identity matrix D isgenerated:

λ_(K+M) ₁ _(+L·t+s)=p_(M) ₁ _(+Q) ₂ _(·s+t) for 0≤s<L, 0≤t<Q₂  (16)

FIG. 6 is a diagram showing an example of the operation of the zeropadding unit shown in FIG. 1.

Referring to FIG. 6, a zero padding operation in the case where theshortening pattern order is [4 1 5 2 8 6 0 7 3] can be seen.

In the example shown in FIG. 6, the length of the LDPC information bitstring is 3240, and thus LDPC information bits include 9 groups eachcomposed of 360 bits.

First, when the number of groups for which all the bits thereof arefilled with 0 is determined using Equation 2, (3240−368/360)=7.9, andthus 7 groups are determined to be the groups for which all the bitsthereof are filled with 0.

Furthermore, since the shortening pattern order is [4 1 5 2 8 6 0 7 3],a total of 7 groups, i.e., a 5th group 610 indexed as 4, a 2nd group 620indexed as 1, a 6th group 630 indexed as 5, a 3rd group 640 indexed as2, a 9th group 650 indexed as 8, a 7th group 660 indexed as 6 and a 1stgroup 670 indexed as 0, are selected, and all the bits of the groups arefilled with 0.

Furthermore, since an 8th group 680 indexed as 7 is next to the 1stgroup 670 indexed as 0, 352 (=3240−368−(360×7)) bits from the beginningof the 8th group 680 indexed as 7 are filled with 0.

After the zero padding has been completed, the BCH-encoded bit string ofN_(bch)(=368) bits is sequentially mapped to a total of 368 bits, i.e.,the 360 bits of the 4th group 690 indexed as 3 and the remaining 8 bitsof the 8th group 680 indexed as 7.

FIG. 7 is a diagram showing an example of the operation of the paritypermutation unit shown in FIG. 1.

Referring to FIG. 7, a parity permutation operation in the case wherethe order of group-wise interleaving corresponding to the sequence [2023 25 32 38 41 18 9 10 11 31 24 14 15 26 40 33 19 28 34 16 39 27 30 2144 43 35 42 36 12 13 29 22 37 17] can be seen.

K_(ldpc)(=3240) information bits are not interleaved, and 36 groups eachcomposed of 360 bits (a total of 12960 bits) become an interleavingtarget.

Since the order of group-wise interleaving corresponds to the sequence[20 23 25 32 38 41 18 9 10 11 31 24 14 15 26 40 33 19 28 34 16 39 27 3021 44 43 35 42 36 12 13 29 22 37 17], the parity permutation unitlocates a 21st group indexed as 20 at a 10th group location 710 indexedas 9, a 24th group indexed as 23 at a 11th group location 720 indexed as10, . . . , a 38th group indexed as 37 at a 44th group location 730indexed as 43, and a 18th bit group indexed as 17 at a 45th grouplocation 740 indexed as 44.

FIG. 8 is a diagram showing an example of the operation of the zeroremoving unit shown in FIG. 1.

Referring to FIG. 8, it can be seen that the zero removing unitgenerates signaling information for transmission by removing zero-paddedparts from the information part of an LDPC codeword.

FIG. 9 is a block diagram showing a zero padding apparatus according toan embodiment of the present invention.

Referring to FIG. 9, the zero padding apparatus according to theembodiment of the present invention includes a processor 920, and memory910.

The processor 920 generates a LDPC information bit string by deciding anumber of groups whose all bits are to be filled with 0 using adifference between a length of the LDPC information bit string and alength of a BCH-encoded bit string (K_(ldpc)−N_(bch)), selecting thegroups using a shortening pattern order to fill all the bits of thegroups with 0, and filling at least a part of remaining groups, whichare not filled with 0, with the BCH-encoded bit string.

In this case, the BCH-encoded bit string may correspond to variablelength signaling information. In this case, the variable lengthsignaling information may be L1-Detail information.

In this case, each of the groups may include 360 bits, the LDPCinformation bit string may include 3240 bits, and the LDPC encoder maycorrespond to an LDPC codeword whose length is 16200 and whose code rateis 3/15.

In this case, the processor 920 may decide a group which is partially tobe filled with 0 using the shortening pattern order, and fill a numberof bits corresponding to a number decided by using the differencebetween the length of the LDPC information bit string and the length ofthe BCH-encoded bit string (K_(ldpc)−N_(bch)) with 0 from the start ofthe group.

In this case, the shortening pattern order may be defined for 9 groupsas shown in the Table 2.

In this case, the shortening pattern order may correspond to an order ofan 8th group indexed as 7, a 9th group indexed as 8, a 6th group indexedas 5, a 5th group indexed as 4, a 2nd group indexed as 1, a 3rd groupindexed as 2, a 7th group indexed as 6, a 4th group indexed as 3, and afirst group indexed as 0.

In this case, the LDPC codeword may be used for parity permutation whichis performed by group-wise interleaving corresponding to an order ofgroup-wise interleaving shown in the Table 3 and a part of parity bitsof the LDPC codeword is punctured after the parity permutation.

The memory 910 provides the LDPC information bit string to an LDPCencoder.

The zero padding apparatus shown in FIG. 9 may correspond to the zeropadding unit 140 shown in FIG. 1.

Furthermore, the structure shown in FIG. 9 may correspond to an inversezero padding apparatus. In this case, the inverse zero padding apparatusmay correspond to the inverse zero padding unit 340 shown in FIG. 1.

When the structure shown in FIG. 9 corresponds to the inverse zeropadding apparatus, the memory 910 receives the LDPC information bitstring from the LDPC decoder.

The processor 920 selects groups whose all bits are filled with 0 usinga shortening pattern order and generates the BCH-encoded bit string fromthe LDPC information bit string using remaining groups exclusive of thegroups.

In this case, the BCH-encoded bit string may correspond to variablelength signaling information. In this case, the variable lengthsignaling information may be L1-Detail information.

In this case, each of the groups may include 360 bits, the LDPCinformation bit string may include 3240 bits, and the LDPC encoder maycorrespond to an LDPC codeword whose length is 16200 and whose code rateis 3/15.

In this case, the shortening pattern order may be defined for 9 groupsas shown in the Table 2.

In this case, the shortening pattern order may correspond to an order ofan 8th group indexed as 7, a 9th group indexed as 8, a 6th group indexedas 5, a 5th group indexed as 4, a 2nd group indexed as 1, a 3rd groupindexed as 2, a 7th group indexed as 6, a 4th group indexed as 3, and afirst group indexed as 0.

FIG. 10 is an operation flowchart showing a zero padding methodaccording to an embodiment of the present invention.

Referring to FIG. 10, the zero padding method according to theembodiment of the present invention includes deciding the number ofgroups whose all bits are to be filled with 0 using a difference betweena length of an LDPC information bit string and a length of a BCH-encodedbit string at step S1010.

In this case, the BCH-encoded bit string may correspond to variablelength signaling information. In this case, the variable lengthsignaling information may be L1-Detail information.

In this case, each of the groups may include 360 bits, the LDPCinformation bit string may include 3240 bits, and the LDPC encoder maycorrespond to an LDPC codeword whose length is 16200 and whose code rateis 3/15.

In this case, the LDPC codeword may be used for parity permutation whichis performed by group-wise interleaving corresponding to an order ofgroup-wise interleaving and a part of parity bits of the LDPC codewordis punctured after the parity permutation.

Furthermore, the zero padding method according to the embodiment of thepresent invention includes selecting the groups using a shorteningpattern order at step S1020.

In this case, the shortening pattern order may be defined for 9 groupsas shown in the Table 2.

In this case, the shortening pattern order may correspond to an order ofan 8th group indexed as 7, a 9th group indexed as 8, a 6th group indexedas 5, a 5th group indexed as 4, a 2nd group indexed as 1, a 3rd groupindexed as 2, a 7th group indexed as 6, a 4th group indexed as 3, and afirst group indexed as 0.

Furthermore, the zero padding method according to the embodiment of thepresent invention includes filling all the bits of the selected groupswith 0 at step S1030.

Furthermore, the zero padding method according to the embodiment of thepresent invention includes generating the LDPC information bit string byfilling at least a part of remaining groups which are not filled with 0,with the BCH-encoded bit string at step S1040.

Although it is not shown in FIG. 10, the zero padding method accordingto the embodiment of the present invention may further include providingthe LDPC information bit string to an LDPC encoder.

Moreover, the zero padding method according to the embodiment of thepresent invention may further include deciding a group which ispartially to be filled with 0 using the shortening pattern order; andfilling the number of bits corresponding to the number decided by usingthe difference between the length of the LDPC information bit string andthe length of the BCH-encoded bit string with 0 from the start of thegroup.

As described above, the zero padding apparatus, the zero padding methodand the inverse zero padding apparatus according to the presentinvention are not limited to the configurations and methods of theabove-described embodiments, but some or all of the embodiments may beselectively combined such that the embodiments can be modified invarious manners.

1. An inverse zero padding apparatus, comprising: memory configured tostore an LDPC information bit string restored from an LDPC decoder; anda processor configured to select groups whose all bits are filled with 0using a shortening pattern order and generate a BCH-encoded bit stringfrom the LDPC information bit string using remaining groups exclusive ofthe groups.
 2. The inverse zero padding apparatus of claim 1, whereinthe BCH-encoded bit string corresponds to variable length signalinginformation.
 3. The inverse zero padding apparatus of claim 2, whereineach of the groups includes 360 bits, the LDPC information bit stringincludes 3240 bits, and the LDPC decoder corresponds to an LDPC codewordwhose length is 16200 and whose code rate is 3/15.
 4. The inverse zeropadding apparatus of claim 3, wherein the shortening pattern order isdefined for 9 groups.
 5. The inverse zero padding apparatus of claim 4,wherein the shortening pattern order corresponds to an order of an 8thgroup indexed as 7, a 9th group indexed as 8, a 6th group indexed as 5,a 5th group indexed as 4, a 2nd group indexed as 1, a 3rd group indexedas 2, a 7th group indexed as 6, a 4th group indexed as 3, and a firstgroup indexed as
 0. 6. An inverse zero padding method, comprising:storing an LDPC information bit string restored from an LDPC decoder;and generating a BCH-encoded bit string from the LDPC information bitstring using remaining groups exclusive of groups whose all bits arefilled with 0 using a shortening pattern order.